This invention relates to radiotherapy devices for treating patients by means of radiation, and more particularly to radiotherapy devices with enhanced dosage concentration upon the affected parts of the body, by which the exposure of operators to the radiation can effectively be prevented.
In accordance with the operation principles, the conventional radiotherapy devices may be classified into two categories: the external irradiation type and the internal irradiation type. The external irradiation type devices include: medical linacs (linear accelerators), 60.degree. C. (cobalt 60) devices, microtrons, and particle beam therapeutic devices. The internal irradiation type devices include those by which the radiation source is encapsulated within a needle, a pin, or a ribbon.
In the case of the external irradiation type devices, the X-ray, the .gamma.-ray, or the electron beam or other particle beams (such as the proton beam and the neutron beam) are irradiated upon the affected part to give the radiation damage thereon so as to treat it. Among them, the proton beam device exhibits relative superiority with respect to the concentration of the radiation at the affected part. In the case of the linac, the electron beam energy level is generally from 4 MeV to 20 MeV, and the range of penetration within the body is from about 1 centimeters to 10 centimeters. In the case of the internal irradiation type, the radiation source such as 226 Ra (radium 226) is sealed within a needle, etc., and is inserted into the affected part of the body of the patient. Thus, these type of devices exhibit superior concentration to the affected part. The usual radiation species include .alpha.-rays, .beta.-rays, and .gamma.-rays.
The conventional radiotherapy devices, however, have the following disadvantage. In the case of the external irradiation type devices such as the medical linacs, 60.degree. C. (cobalt 60) devices, and microtrons, the concentration of the dosage upon the affected part is often insufficient. Further, in the case of the therapeutic devices using particle beams, the buildings for accommodating the accelerators, etc., may become extremely expensive. Thus, as shown in Japanese Utility Model Publication (Kokoku) No. 44-19999, for example, the device can hardly be used for everyday therapeutic purposes.
In the case of the internal irradiation type devices, on the other hand, the operator may be exposed to radiation upon insertion of the radiation source into the body of the patient. Further, the attenuation of radiation is rapid and it is difficult to obtain a high dosage level. Furthermore, the maintenance of the radiation source incurs trouble. For the purpose of effecting an appropriate therapy suited to the patient's conditions, a good number of radiation source species is necessary.